This invention relates to a data recovery system for use in a data processing or computer system which is used for carrying out data processing in compliance with a transaction processing program on data blocks memorized in a data file on a block by block basis.
Various data recovery systems are already known. The data recovery system is used for recovering those of the data blocks which are damaged or otherwise adversely affected in the data file due to a system failure or system down. In other words, the data recovery system is used for carrying out data recovery on the data blocks which should be recovered into recovered blocks. For such a data recovery system, the data processing system is operable in combination with the data file and a recovery log file. The transaction processing program specifies data retrieval and data renewal among others. The data processing system comprises a block memory area, an activation controlling arrangement responsive to a first control signal for controlling activation of the transaction processing program, a block transferring arrangement for transferring data blocks during the data retrieval from the data file to the block memory area for storage therein as memorized blocks, a block retrieving arrangement for retrieving during the data retrieval those of the memorized blocks from the block memory area for data processing in compliance with the transaction processing program which are specified by the transaction processing program, a data updating or renewing arrangement for updating during the data renewal those of the memorized blocks in the block memory area into updated blocks which are specified by the transaction processing program, and a log storing arrangement coupled to the data updating arrangement for storing log data in the recovery log file upon renewal of the memorized blocks in the block memory area into the updated blocks. The data recovery system includes a log memory area, a log transferring arrangement for transferring the log data from the recovery log file to the log memory area, and a block storing arrangement for storing during the data renewal and the data recovery the updated and the recovered blocks in the data file from the block memory area. The data recovery is carried out on restarting or rerunning the transaction processing program after occurrence of the system failure.
In a conventional data recovery system, the transaction processing program is again activated after completion of the data recovery. It is to be noted in this connection that some of the data blocks need not be recovered even for an occurrence of the system failure and can be processed before completion of the data recovery of the data blocks which must be recovered.